Spark plug



Marcm, 1932. H. ABEzzANA 1,848,065

Filed Oct. l0, 1929 (g1/wanton Patnie Mar. 1, 1932 U1\u'l1:nf STATESPri'rriu'r oFFicE HECTOR RAIBEZZANA, OF FLINT, MICHIGAN, ASSIGNORVTO A CSPAiR/K PLUG COMPANY, F F/LINTAMICHIGAN, A. COMPANY OF MTCHTGALN' SPARKPLUG y Application ledctober 10, 1929. ASerial No. 398,66@

This invention relates to spark plugs of the type commonly used ininternal combus tion engines. Such .plugs are usually composed of ametal shell adapted to befthreadedl into the engine, and aninsulatingmember of porcelain, mica orother suitable material, 1n whichis carried an electrode member. These insulators are necessarilysubjected to the very high temperatures developed 1n the combustionchamber, and in order to avoid the possibility of their becoming crackedor otherwise damaged from excessively high temperatures, it is essentialthat provision be made to .carry away or dissipate as much of theheat aspossible. In the usual type of plug, the heat is transferredfromthe'insu-v lator to the shell, and 'from the latter to the engine, byconduction. Due to the fact thatv the threaded connection betwen theshell and` the engine interferes to a considerable extent with the rapidtransfer of the heat, the insulator under certain conditions becomesexcessively hot and as a result crackstthereby rendering the spark pluginoperatlve.

It is therefore an object of this invention to provide a spark plugconstruction in which the heat may be more readily and positively ,1'transferred to the combustion chamber wall,

t from which it may be carried away by the 130 liquid in the coolingsystem. This is accomplished by eliminating the usual spark plug shell,thereb allowing the insulating member to come into direct contactwiththe wall of the combustion chamber. A tapered aperture is formed in theWall and the insulating member'is correspondingly tapered so that it mabe wedged into close contact with the wa l in order to insure amorepositive and rapid transfer of the heat by conduction.

By rotating the insulating member in the tapered aperture at the time ofassembly,

with any suitable grinding compound placed between the two, the surfacesmay be ground to exactly the same shape, similar to the manner in whichvalves are ground on their seats. Thus the maximum possible area ofcontact between the insulator and the com-v A bustion chamber wall isobtained, and the `conduction of heat from the lformer to the 5 latteris facilitated.

. 1, but showing modi-fied forms of spark plugs.

Another object of the invention is to construct a spark plug in which itis not necessary to provide the usual gaskets for preventing leakage ofthe gases from the cylinder. Such gaskets sometimes permit leakage ofgas after the spark plug has been in use, due to the continual expansionand contraction of the shell relative tothe insulating member. Due tothe fact that the surfaces of the tapered aperture and the insulator inmy improved spark plug are ground together to form a perfect seat, thereisno possibility of leakage occurring between the two. By eliminatingthe gaskets and the usual metal shell, the cost of the plug ismaterially reduced. Y

Other objects and advantages will be apparent upon referring to thespecification and accompanying drawings, in which:

Fig. 1 is a section through a portion of a combustion chamber wall,showing my imlproved spark plug assembled therein.

Fig. 2 is a section taken on the line 2-2 of Fig. 1.

'Figs 3-7 are views corresponding to Fig. 75

The reference numeral 10 indicates a portion of an internal combustionengine which j forms one wall of the combustion chamber. A cooling waterjacket 12 is formed between 8o the wall 10 and an outer wall 14. Anaperture 16 is formedr throughl both the walls for the purpose ofpermitting the insertion of a spark plug. This spark plug consists of aninsulating member 18 formed o f porcelain, mica or any other suitablematerial. A portion 20 of this member is tapered and fits into acorrespondingly tapered portion 22 formed in a combustion chamber wall.The usual central electrode 24; is supported in the .insulating member.The lower end 2 6 of. this electrode'is bent at a right angleto the mainportion and extends quite 4close to a boss 28 formed on the inside ofthe combustion chamber wall 10.l The distance between the'end 26 of theelectrode and the boss 28 is so set as to be exactly the same as thewidth of the spark gap in the ordinary type of spark plug. f f

-At the time the insulating member 18 is 1 alim mi assembled in theaperture 16, it is pret-erably ground in place with any suitablegrinding compound placed between the tapered portions 20 and 22. Theinsulating member 18 is rotated sufficiently to insure that the sur-'laces will be ground to exactly the same shapes so that the entiresurface ol' the tapered portion 20 will be in contact with the taperedportion 22, thus insuring the maximum possible area ot contact, whichwill permit a large amount ot heat to be conducted into the combustionchamber wall from which it is removed by the circulation ot th-e coolingwater in the jacket 12.

Any suitable means may be provided for holding the insulator in place inthe apern ture 18. ln Fig. 1 there is illustrated a quick detachabletype of holding means, which consists of a gland nut 3() threaded intothe wall 14, and/or which may be permanently secured therein in anysuitable lmanner such as by welding. llhis gland nut has -lormed on it aplurality of projections 32 which engage cam surfaces 34 'formed on theinsulating member 18. Slots 36 are formed in the body portion ot theinsulating member to permit the latter to be inserted through the glandnut 30, the slots being of a sli htly greater width than the projections32. liter this has been done, the insulating member is rotated and thecam surfaces 34 engage the projections 32 and serve to wedge the taperedportion 20 of the insulating member into firm contact with the taperedportion 22 of the aperture 16. Obviously this wedging action not onlyserves to bring about a better transfer of heat from the insulatingmember 18 to the combustion chamber wall, but also provides a tight sealbetween the two which prevents the escape of any of the explosive gasesin the combustion chamber. The result is that no gaskets are needed asis the case in the usual type of spark plug.

In the form of plug shown in Fig. 3, a shoulder 38 is formed on theinsulating member 40. The gland nut'42 in this construction bearsagainst a sleeve 44 formed of copper or any other suitable materialhaving a comparatively high coefficient of expansion. The opposite endof the sleeve 44 bears against the shoulder 38, and it will be readilyseen that as the parts become heated and tend to expand, the sleeve 44will expand more rapidly than the gland nut 42 and the combustionchamber wall, and will consequently serve to maintain a firm contactbetween the tapered portions of the insulator and the combustion chamberwall at all times,'there by preventing leakage of the explosive gasesand bringing about a more uniform transfer of heat from the insulatingmember to the combustion chamber Wall.

In the form shdwn in Fig. 4, the lower end of the central electrode 46is not bent, but is spaced the desired distance above a ground reagentelectrode member 48 secured in a boss till formed on the inside o'l thecombustion chamn ber wall. A. slightly diderent form 4oil holdingmechanism is shown in connection with this form. This consists or aliulcrum member 52 having an end 54 adapted to bear against theinsulator member 56. The opposite end of the Eulerum lmember bearsagainst the wall 14 or it desired against the insulator of another sparkplug. A nut 58 threaded on a stud 60 serves to draw the l'i'ulcrummember against the insulator 56, thereby wedging the latter into tirmcontact with the tapered aperture in the combustion chamber wall. ln

this term a more rapid transfer oi? heat is provided tor as well as abetter seal, due to the increased area oit the tapered surfaces.

ln Fig. 5 is shown an insulating member 52 in which are supported twoelectrodes 64 and '66. rlhis type oi' plug is more likely to be used inengines ot the type wherein two spark plugs are provided for eachcylinder, these plugs being connected in series with each other toinsure that a spark will be produced in both plugs. ln this type otinstallation the electrode 64 is connected to the distributor and theelectrode 66 is connected to the other spark plug.

lnthe form shown in Fig. 6 a central elec trode 68 is spaced the desireddistance away from a second electrode l0 which is supported in theinsulating member 72 in such a position that it contacts with the wallot the combustion chamber at "(4. An advantage of this .type ofconstruction is that the widthot` the spark gap may be definitelydetermined betore the plug is assembled in the aperture.

In Fig. 7 a slightly different form o plug is illustrated, wherein theinsulating member 76 is composed of layers of mica, there bein# anaxially extending insulating sleeve 7 8 o micasurrounding the centralelectrode 80. The lower portion 82 of the insulating member is taperedto fit into a tapered aperture 84, while av metal sleeve 86 surroundsthe upper portion of the insulating member. Additional mica insulation88 surrounds the electrode and the axially extending insulation 78 abovethe sleeve 86. A gland nut 90 threaded into the Wall 14 engages thesleeve 86 and serves to wedge the tapered portion 82 of the insulatingmember 76 into firm contact with the tapered aperture 84, to eii'ect a.tight seal and a rapid conduction of heat from the insulating member tothe combustion chamber wall.

It will be understood of course that in all of the forms of plugs shownand described itis preferable to grind the tapered portions of theinsulating members into place in the tapered apertures to insure aslarge an area of contact as possible, in ord-er that there may be a moresatisfactory transfer of heat and at the same time to provide agas-tight seal. Obviously, any of the securing means shown may be usedwith any of the types of spark lugs. p Itis thought from the foregoing,taken in connection with the accompanying drawings, that theconstruction and operation o the spark plug will be apparent to thoseskilled in the art, and that various changes in size, shape, andproportion may be made without departing from the spirit and scope ofthe l0 appended claims.

' I claim:

1. In combination, a combustion chamber wall having therein a spark plugreceiving opening, at least a portion of which is of conical shape, aninsulator body receivable within said opening and having a conicalshapedperipheral surface for engagement with the conical portion of theopening, an inwardly extending tongue at the opening, 9,0 and a camsurface fon said body for engagement with said tongue to move theconical part into tight contact.

2. In combination, a combustion chamber wall having therein a spark plugreceiving .5 opening, at least a portion of which is of conical shape,an insulator body receivable within said opening and having aconical-shaped peripheral surface for engagement with the conicalportion of the opening, a series of 9,0 inwardly extending tongues atthe opening, slidable through axially extending ways in the surface ofsaid body, and a cam surface adjacent each way for engagement with thetongue upon rotation of the body to bring the conical parts into tightcontact.

In testimony whereof I affix 1n signature.

HECTORILAB ZZANA.

